Share-Based Compensation (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	0 Months Ended	6 Months Ended
	Mar. 06, 2013	Jun. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting age, minimum		60 years
Employee service, continuous minimum service		5 years
Minimum period shares have been granted prior to retirement before shares fully vest		6 months
Compensation expense recognition period, minimum		6 months
Compensation expense recognition period, maximum		36 months
Compensation expense over a remaining weighted-average period		1 year 10 months 24 days
Unrecognized compensation cost related to nonvested share-based compensation arrangements		$ 45.3
Restricted Stock Units and Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of restricted stock and stock appreciation rights granted	25.2
Aggregate grant date fair value, net of estimated forfeitures1	24.2
Requisite service period	2 years 4 months 24 days
Performance Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target value of shares granted during the period (in dollars per unit)	$ 100
Awards vesting period	3 years
Total shareholder return, Minimum	0
Total shareholder return, maximum	11.6
Vesting percentage based on relative total shareholder return ranking on annual basis		25.00%
Vesting percentage of performance units periodically (in hundredths)		25.00%
Grant date fair value of P-Units		$ 5.8
Performance measurement period		3 years
Vesting percentage of performance units (in hundredths)		25.00%